The overall objective of this proposal is to investigate specific interactions between adenovirus and cellular gene products that lead to the regulation of viral early gene expression, cellular transformation, and progression of the transformed cell phenotype. The latter process, progression, will lead to studies aimed at the isolation and characterization of two classes of cellular progression genes whose expression modulates the regulation of the transformed cell phenotype. These include 1) Those genes which directly initiate the cascade of regulatory events leading to the stable genetic progressed phenotype, 2) Those genes which are secondarily regulated along the pathway leading to the progressed cellular phenotype. What makes the experimental approaches described in this proposal unique is that the intact viral genome and its cis affects on viral gene expression have been considered, and a genetically defined and stable panel of Ad5-transformed cell lines at various stages of transformation progression have been isolated. The specific aims of the proposal are: 1. To investigate whether changes in viral and/or cellular gene expression (at the level of both transcriptional and post- transcriptional control) are responsible for the stepwise progression of the transformed cell phenotype. 2. To investigate the mechanism(s) by which viral E1B proteins dictate the pathway leading to the establishment of the transformed cell phenotype, by the isolation of viruses containing mutations affecting specific combinations of E1A and E1B proteins in rodent cell transformation assays. 3. To investigate whether the rate of viral E1A gene expression will alter the ability of viruses to transform permissive human cells and nonpermissive rodent cells. 4. To investigate whether E1B transcription initiation is potentiated by the rate of overlapping E1A transcription, both in vivo and in vitro.